I've never liked shell gas for 1 reason, but today 2.
the first being, it always costs more no matter what.
the second stems for my Ranger
the people who owned my truck before me used shell exclusively, they had to put 92 (at the time) octane in. When I bought it from them, they told me if I didn't use 92, the motor would ping constantly.
So after the tank emptied out, I decided to test that theory and I put Unocal 76 regular unleaded in. Not one problem.
after that tank, I put 10 gallons of shell regular unleaded (87) in, and yes, I noticed a ping.
I burned 5 gallons up, and filled up on Unocal 76 regular unleaded.
the pinging stopped. Next 3 tanks were Unocal.
I then went to Arco because I was out of town and didn't want to use Shell. Not one problem.
Well fast forward 15 years, I use cheap fuel, Costco mainly, Valero if I'm deathly low (cuz a valero station is across the street from me). No pinging, no problems.
However, where I live, there's 3 gas suppliers, shell, chevron and this one called golden eagle. Of these 3 refineries, I know that wherever you go, you're getting one of these fuels.
You get the same gas, but their proprietary additives.
So all you can do is hope you're getting what you're getting.